X:
Y:
You will see the total below:
You can use the Output property of CallbackEventArgs in the Callback event handler in order to override the default rendering mechanism of the UltimateAjax control on the server-side.

When you check OverrideOutput it will not render the contents of the UltimateAjax control, but only the label that shows the total. Therefore you won't see the "You will see the total below:" line above the total.

You can also override the default rendering on the client-side as you can see in the CallbackResult sample.